The overturned bus lies off the side of the Phimai-Talat Khae road in tambon Nai Muang on Sunday night. (Photo by Prasit Tangprasert)

Twenty-two people were injured, one of them seriously, when a tour bus collided with a pickup truck in heavy rain in Phimai district late on Sunday night, police said.

Pol Capt Panya Patangsewa, of Phimai police, said the accident occurred about 11pm between kilometre markers 2 - 3 in front of a PTT petrol station on the Phimai - Talat Khae road in tambon Nai Muang.

Winij Munon, 51, the driver of the bus, told police it was raining heavily at the time of the accident. The pickup had suddenly changed lanes, cutting in front of the bus, which ran into the back of it and sent it into the roadside ditch.

Mr Winij said he lost control of the bus, which overturned and ended up lying on the other side of the road.

The bus was taking 43 passengers to Bangkok from Suwannaphum district of Roi Et province.

Twenty-two people in the two vehicles were injured, including the pickup driver Somnuek Klongjai, 33, and his four-year-old son. Mr Somnuek suffered serious head injuries. All of the injured were admitted to Phimai Hospital.

The Nakhon Ratchasima municipal area was pelted by heavy rain for about one hour on Sunday night, starting about 7pm. Many spots in the municipality were covered with water up to 30 centimetres deep.

They included areas in front of the Save One Market and The Mall department store on Mitraphap Road, the Wat Mai Ampawan intersection on Mukkha Montree Road, the IT Plaza intersection on Ratchadamnern Road and Det-udom Road.

Municipal workers were sent to clear garbage that was blocking drains and preventing the water draining off. The roads were later reported to have dried out.